This project is an extension of our work to improve the recognition and understanding of a clinically significant and prevalent Eating Disorder Not Otherwise Specified, "Purging Disorder" (PD). PD is characterized by recurrent purging after normal or small amounts of food in individuals of normal weight who experience body image disturbance. This project examines the proposal that one set of psychological and physiological mechanisms (deficient satiation and blunted gut peptide, ghrelin and PYY, responses to food intake) is particularly associated with bingeing, and that a separate set of alterations (excessive satiation, gastrointestinal distress and delayed gastric emptying) is linked to purging. By examining factors differentially associated with binge eating vs. purging, this new study can contribute to the development of pharmacological treatments for eating disorders, particularly PD - a newly characterized disorder for which no evidence-based treatments exist. The new study also will add necessary information for evaluating the validity of defining PD within diagnostic systems. Participants will include women with PD (n=25), bulimia nervosa purging subtype (BNp;n=25), BN nonpurging subtype (BNnp;n=25), and healthy female controls (n=25). During a 1st study visit, participants will complete structured clinical interviews, questionnaires, and medical exams for evaluation of clinical features and eligibility. During a 2nd study visit, participants will consume an ad lib test meal. Results will show whether BNp and BNnp (both characterized by recurrent bingeing) demonstrate deficient satiation compared to controls and whether PD demonstrates excessive satiation compared to controls. During a 3rd and 4th visit, participants will consume a fixed test meal and undergo an experimental manipulation of gastric emptying using a single 10 mg oral dose of metoclopramide in a double-blind, placebo-controlled cross-over design. Results from the fixed meal + placebo condition will be used to examine whether BNp and BNnp demonstrate blunted ghrelin and PYY responses relative to controls and PD and whether PD and BNp (both characterized by recurrent purging) demonstrate increased gastrointestinal distress and delayed gastric emptying relative to controls and BNnp. Finally, the comparison of groups in the fixed test meal + placebo vs. fixed test meal + metoclopramide conditions will be used to test whether increased gastric emptying causes reductions in gastrointestinal distress in PD relative to the other groups. All 4 visits will occur in the University of Iowa's Institute for Clinical and Translational Science, funded by an NIH Clinical and Translational Science Award. Our psychobiological focus will allow us to translate basic research discoveries on the effects of gut peptides and gastric emptying on satiation into explanatory models for factors that contribute to the development or maintenance of BN and PD and will contribute to the development of effective pharmacological treatments for these dangerous disorders of eating. PUBLIC HEALTH RELEVANCE: Eating disorders represent significant mental health problems that affect over 5 million people in the United States. The proposed work will enhance treatment efforts by identifying psychobiological factors that contribute to the development of binge eating versus purging, core features of most eating disorders.